Calcium acetate, magnesium acetate and calcium magnesium acetate have recently been the subject of study for use as deicing agents to replace conventional road salt and calcium chloride, both of which have been shown to have undesirable corrosive and environmentally detrimental properties. Among these materials calcium magnesium acetate (CMA) has particularly been the subject of study and efforts have been made to produce it on a commercial scale. See U.S. Pat. Nos. 4,426,308, 4,444,672, 4,511,485 and 4,606,836.
However, a disadvantage to commercially produced CMA has thus far prevented its use as a deicing agent for airport runways and taxiways. It has been found that commercial CMA stains or corrodes the aluminum and aluminum alloys used on aircraft. Unacceptable levels of corrosion to these metals, particularly to aluminum itself, could affect the functioning of the mechanical components as well as the structural integrity of the aircraft.
The currently accepted airport runway deicing compositions are ethylene glycol and urea; however, both have been subject to criticism because of their adverse environmental effects. For example, urea may contaminate lakes and streams and is detrimental to fish and other aquatic life. Therefore, in that the currently acceptable deicing compositions used on airport runways and taxiways are under severe criticism for their environmental disadvantages, and being that other conventional solid deicing compositions used on roads, including previously available CMA, have unacceptable corrosivity for aluminum and aluminum alloys, there is need to develop an alternative deicing composition specifically for use on airport runways and taxiways. To reduce the staining effect of commercial CMA, it has been found to be necessary to use additives (such as chelating compounds).
It is therefore an object of the present invention to provide novel deicing compositions which are useful on airport runways and taxiways.
It is a further object of the present invention to provide a lower cost method of preparing large particles of substantially pure calcium magnesium acetate which do not stain aluminum and do not require anti-staining additives.
These and other objects of the invention will be apparent from the following description and from the practice of the invention.